[Bugfix] Robust Qwen3 Coder streaming: fragmented tags, speculative decoding fixes, and content tracking

tests/tool_parsers/test_qwen3coder_tool_parser.py

@@ -1146,3 +1146,50 @@ def test_no_double_serialization_string_args(qwen3_tool_parser):
     args = json.loads(raw_arguments)
     assert args["message"] == "hello world"
     assert '\\"hello world\\"' not in raw_arguments
+
+
+def test_extract_tool_calls_streaming_split_tag(qwen3_tool_parser):
+    """
+    This highlights the need to use current_text instead of delta_text.
+    """
+    request = ChatCompletionRequest(model=MODEL, messages=[])
+
+    # Iteration 1: "<tool"
+    prev_text_1 = "I will use a tool."
+    delta_text_1 = "<tool"
+    curr_text_1 = prev_text_1 + delta_text_1
+
+    msg1 = qwen3_tool_parser.extract_tool_calls_streaming(
+        previous_text=prev_text_1,
+        current_text=curr_text_1,
+        delta_text=delta_text_1,
+        previous_token_ids=[1, 2, 3],
+        current_token_ids=[1, 2, 3, 4],
+        delta_token_ids=[4],
+        request=request
+    )
+
+    # Iteration 2: "_call>"
+    prev_text_2 = curr_text_1
+    delta_text_2 = "_call>"
+    curr_text_2 = prev_text_2 + delta_text_2
+
+    msg2 = qwen3_tool_parser.extract_tool_calls_streaming(
+        previous_text=prev_text_2,
+        current_text=curr_text_2,
+        delta_text=delta_text_2,
+        previous_token_ids=[1, 2, 3, 4],
+        current_token_ids=[1, 2, 3, 4, 5],
+        delta_token_ids=[5],
+        request=request
+    )
+
+    # The assertion must verify that the is_tool_call_started variable correctly switches to True
+    assert qwen3_tool_parser.is_tool_call_started is True, "is_tool_call_started should be True when '<tool_call>' is completed in current_text."
+
+    # and that the function does not return fragments of the tag in DeltaMessage(content=...)
+    if msg1 and msg1.content:
+        assert "<tool" not in msg1.content
+    if msg2 and msg2.content:
+        assert "_call>" not in msg2.content
+

vllm/tool_parsers/qwen3coder_tool_parser.py

@@ -25,7 +25,7 @@
     Tool,
     ToolParser,
 )
-from vllm.tool_parsers.utils import find_tool_properties
+from vllm.tool_parsers.utils import find_tool_properties, partial_tag_overlap
 
 logger = init_logger(__name__)
 
@@ -109,6 +109,7 @@ def _reset_streaming_state(self):
         # Store accumulated parameters for type conversion
         self.accumulated_params = {}
         self.streaming_request = None
+        self._sent_content_idx = 0
 
     def _convert_param_value(
         self, param_value: str, param_name: str, param_config: dict, func_name: str
@@ -391,29 +392,39 @@ def extract_tool_calls_streaming(
         # Handle normal content before tool calls
         if not self.is_tool_call_started:
             # Check if tool call is starting
+            tool_starts_count = current_text.count(self.tool_call_start_token)
             if (
                 self.tool_call_start_token_id in delta_token_ids
-                or self.tool_call_start_token in delta_text
+                or tool_starts_count > self.current_tool_index
             ):
                 self.is_tool_call_started = True
                 # Return any content before the tool call
-                if self.tool_call_start_token in delta_text:
-                    content_before = delta_text[
-                        : delta_text.index(self.tool_call_start_token)
-                    ]
+                last_start = current_text.rfind(self.tool_call_start_token)
+                if last_start > self._sent_content_idx:
+                    content_before = current_text[self._sent_content_idx:last_start]
+                    self._sent_content_idx = last_start
                     if content_before:
                         return DeltaMessage(content=content_before)
                 return None
             else:
+                overlap = partial_tag_overlap(current_text, self.tool_call_start_token)
+                sendable_idx = len(current_text) - overlap
+
                 # Check if we're between tool calls - skip whitespace
                 if (
                     current_text.rstrip().endswith(self.tool_call_end_token)
                     and delta_text.strip() == ""
                 ):
                     # We just ended a tool call, skip whitespace
+                    self._sent_content_idx = len(current_text)
                     return None
-                # Normal content, no tool call
-                return DeltaMessage(content=delta_text)
+
+                if sendable_idx > self._sent_content_idx:
+                    content = current_text[self._sent_content_idx:sendable_idx]
+                    self._sent_content_idx = sendable_idx
+                    if content:
+                        return DeltaMessage(content=content)
+                return None
 
         # Check if we're between tool calls (waiting for next one)
         # Count tool calls we've seen vs processed